Vacuum cleaners are widely used for picking up dirt and debris. A vacuum cleaner therefore includes a motor and impeller that together generate a vacuum airflow. A powered brushroll is rotated by a motor and functions to dislodge dirt and debris on an underlying surface and propel the dirt and debris into the vacuum airflow. The brushroll therefore is an important device for enhancing the cleaning ability of a vacuum cleaner.
A vacuum cleaner can be used on a variety of underlying surfaces. For example, the vacuum cleaner and powered brushroll can be used to pickup dirt and debris on carpeting. Furthermore, the vacuum cleaner and powered brushroll can be used to pickup dirt and debris deep down among carpet fibers. Alternatively, the vacuum cleaner and brushroll can be used on hard, flat surfaces, such as wood floors, tile, linoleum, etc. These underlying surfaces can vary greatly in their firmness, flatness, evenness, texture, etc. Because of variations in firmness, the wheels of the vacuum cleaner can sink into the surface, such as a carpeted surface, and the distance from the brushroll to the surface can change. Because the bristles of the brushroll are of a fixed length, this height variation will undesirably affect the amount of contact between the brushroll and the underlying surface.
In the prior art, the most common approach is to have a brushroll of a fixed height. Therefore, when moving from a hardwood floor to a carpet, when moving from a carpet to a hardwood floor, or when moving from a carpet of one depth and density to another carpet having a different depth and density, the height of the brushroll from the underlying surface will change. As a result, the effectiveness of the brushroll will be greatly impacted.
In another prior art approach, the wheels of the vacuum cleaner are adjustable and the entire vacuum cleaner can be raised and lowered. Although this accommodates different underlying surfaces and/or textures, the consequence of changing the height of the entire vacuum cleaner is that the distance of the nozzle and therefore the vacuum airflow is changed in relation to the underlying surface. This will unfortunately affect the cleaning power of the vacuum airflow and therefore of the vacuum cleaner.